Stormwater containment assembly and associated end section

ABSTRACT

An end section or cap for a stormwater containment assembly includes a substantially half-dome-shaped body member and a connector disposed on the body member along a periphery or perimeter thereof, for coupling the body member to a stormwater chamber wall. The body member has a smooth convex outer surface with an absence of reinforcement ribs and also has a smooth concave inner surface with an absence of reinforcement ribs.

BACKGROUND OF THE INVENTION

The present disclosure relates to a fluid management system. More particularly, the present disclosure relates to a stormwater containment system, exemplarily utilizable beneath a parking lot. This disclosure also relates to an end cap or end section that is a component part of the stormwater containment system.

Stormwater containment systems are used to facilitate the disposal of water run-off which occurs during rain storms. Such systems may be used anywhere that the land use is enhanced by such application. In large cities where land values are high developers are motivated to go to underground containment. In some areas, mosquito control or aesthetics may motivate a developer to go underground even outside large cities.

Such containment systems include arched or vaulted chambers, pipe systems or other crate type modular structures that are built into the base of parking lots and streets for receiving and temporarily housing stormwater run-off. Such a system is disclosed in U.S. Pat. No. 7,118,306 to Kruger et al., U.S. Pat. No. 7,237,981 to Vitarelli, and U.S. Patent Application Publication No. 2007/0081860 by Goddard et al.

A problem with existing stormwater containment systems of the above-referenced kind is that the end sections are sometimes prone to failure. End sections constitute the end walls of the arched or vaulted containment chambers. End sections are typically reinforced along an inside surface with inwardly projecting ribs. Reinforcement structures may also be provided along the outer surfaces of the end sections. Reinforcement ribs typically extend to the edges of the end sections and serve to transmit tensile and compression forces. Reinforcement ribs and other reinforcement structures concentrate tensile and/or compressive stresses and channel the stresses along paths defined by the ribs. The ribs and other reinforcement structures are viewed as necessary to accommodate and support the immense weight of overlying soil and asphalt layers that creates both vertical and horizontal forces on the end section.

SUMMARY OF THE INVENTION

The present invention contemplates an improvement in stormwater containment systems wherein the end caps or end sections are smooth domed members with inner and outer surfaces that are free of reinforcement ribs and preferably free of other structures that extend over such a distance as to prevent a substantially uniform stress distribution.

An end section for a stormwater containment assembly comprises, in accordance with the present invention, a substantially half-dome-shaped body member having a smooth convex outer surface with an absence of reinforcement structures and further having a smooth concave inner surface also with an absence of reinforcement structures. The end section further comprises a connector disposed on the body member along a periphery or perimeter thereof, for coupling the body member to a stormwater chamber wall.

More particularly, an end section body member in accordance with the present invention is free of projecting reinforcement ribs on both the inner concave surface and the outer convex surface. In a preferred embodiment of the invention, the end section body member is free of any projecting structures that extend over such a distance as to prevent a substantially uniform stress distribution. When the end cap is manufactured from polyethylene material, the elimination or reduction of tensile stresses is most important since polyethylene fails from a phenomenon known as environmental stress cracking where in the presence of tensile stresses, cracks may initiate at any scratch, flaw or sharp angle point such as at the intersection of reinforcements, then propagate under the tensile stress driving force until the structure fails.

Recesses may be provided in the outer surfaces of the end section body members to function as handgrips for handling of the end sections. The handgrip formations do not give rise to a build-up of internal stresses. The handgrips are not so large as to interfere with a substantially uniform tensile stress distribution. Coupling corrugations extend along the periphery or edge of the end section, parallel to an edge of the end section. The corrugations function to couple the end section to vaulted main bodies or chamber walls of stormwater containment systems.

Accordingly, a stormwater-chamber end section in accordance with the present invention distributes loads throughout the body of the end section and substantially reduces tensile stresses. Localized tensile stresses do not build up at any point within the end section but instead are directed uniformly to the periphery or perimeter of the end section and transmitted therethrough to the stormwater chamber wall.

In an end section in accordance with the present invention, soil loads on the outside surface of the end section are carried more uniformly by the end section without the stress concentrations that otherwise occur at the reinforcement structures. Moreover, without reinforcing ribs, loads carried by the end section are more evenly distributed around the periphery or perimeter of the end section and ultimately through the abutting chamber to the surrounding soils.

In an end section in accordance with the present invention, the end section has more freedom to deform slightly under the soil load. As the end section or cap deforms, the surrounding soils coalesce in an arched formation and carry loads that would otherwise be carried by the end section. Although reinforced shells in their entireties may be flexible, the present end section is uniformly more flexible than the reinforced shell so that any particular area of the present end section is more flexible and there are no stress risers as there are no reinforced areas.

In accordance with further features of the present invention, the connector is an elongate corrugation integral with the body member along the periphery or perimeter thereof and dimensioned to fit over a terminal lip or rib of the chamber wall. The corrugation cooperates with the lip or rib to loosely couple the body member to the chamber wall to allow for slippage between the corrugation and the lip or rib in a direction radial with respect to the chamber wall and the body member and transverse to the corrugation and the lip or rib.

In an end section pursuant to the present invention, soil arching also arises around the perimeter of the shell. Loads from the end section are transferred to the abutting chamber at the web of the corrugation. Since the end section is a separate component, not integral to the chamber or bonded in any way to the chamber, the end section is allowed to slip at the bearing surface against the abutting chamber. The perimeter of the end section is accordingly allowed to move radially outwardly and upwardly, relieving load in the end section. Additional movement in the direction of the load, away from the load, occurs as the web of the chamber lip, rib or corrugation bends slightly. Solids around the corrugation ultimately resist loads carried in compression by the crest of the corrugation of the chamber. Similarly, solids around the perimeter of the end section limit the outward radial movement. Infinite slippage with no radial support would eventually lead to a loss of compressive strength and failure by bending. Like surrounding soils limiting the movement of the chamber, the perimeter soil support limits the outward movement of the perimeter.

In the design of thermoplastic structures, the reduction of stresses in the plastic is a key objective since plastics creep under continuous load. In the end section of the present invention, long-term creep is managed and used to advantage to develop soil arching and ultimately relaxation of stresses in the end section. The key advantage of avoiding stress concentrations by elimination of reinforcement ribs is especially beneficial when the end section is made of polyethylene. Polyethylene exhibits a behavior of cracking under sustained tensile stress. The end section of the present invention minimizes tensile stresses and carries loads by acting primarily in compression.

Pursuant to a further feature of the present invention, the corrugation defines a longitudinally arcuate cross-sectionally tapered channel receiving the lip or rib on the chamber wall, which itself may take the form of a corrugation.

The body member of an end section in accordance with the present invention has a half dome shape with a pair of arcuate edges, the connector or corrugation being disposed along an upper one of the edges.

An end section for a stormwater containment assembly comprises, in accordance with a particular embodiment of the present invention, a substantially half-dome-shaped body member having a smooth convex outer surface with an absence of outwardly projecting reinforcement ribs thereon and further having a smooth concave inner surface with an absence of inwardly projecting reinforcement ribs thereon. The end section further comprises an elongate longitudinally arcuate corrugation integral with the body member along an edge or perimeter thereof.

Reinforcement structures, particularly ribs, typically extend to the edges of the end sections and serve to transmit tensile and compression forces. Reinforcement ribs and other reinforcement structures concentrate tensile and/or compressive stresses and channel the stresses along paths defined by the ribs. The ribs and other reinforcement structures are viewed as necessary to accommodate and support the immense weight of overlying soil and asphalt layers that creates both vertical and horizontal forces on the end section.

A stormwater containment assembly in accordance with the present invention comprises a chamber member having an arched or vaulted wall and an end section including a substantially half-dome-shaped body member and a connector disposed on the body member along a periphery or perimeter thereof, for coupling the body member to the arched or vaulted wall. The dome shaped body member has a smooth convex outer surface with an absence of reinforcement structures thereon and further has a smooth concave inner surface with an absence of reinforcement structures thereon. More specifically, the smooth convex outer and inner surfaces of the body member are devoid of structures that span the body member, i.e., that extend from one edge to an opposing edge of the body member so as to carry or channel stresses across the body member from an upper side to a lower side thereof.

In one embodiment of the present invention, the inner and outer surfaces of the end section body member are completely smooth and respectively free of inwardly and outwardly projecting ribs of whatever kind.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective disassembled view of a stormwater containment system in accordance with the present invention.

FIG. 2 is a side elevational view of a vaulted or arched main body section of the stormwater containment system of FIG. 1.

FIG. 3 is a side elevational view of an end cap or end section of the stormwater containment system of FIG. 1.

FIG. 4 is a partial vertical longitudinal cross-sectional view of the stormwater containment system of FIG. 1.

FIG. 5 is a schematic vertical cross-sectional sectional view of an earthworks structure incorporating the stormwater containment system of FIGS. 1-4.

DETAILED DESCRIPTION

FIG. 1 shows a stormwater containment system 10 including a vaulted or arched main chamber section 12 and a domed end cap or end section 14, both made of plastic materials. Generally, acceptable thermoplastic materials include virgin impact-modified polypropylene copolymers, virgin high molecular weight or medium molecular weight polyethylene or impact-modified polypropylene copolymers with recycled content or high density or medium density polyethylene with recycled content. In a preferred embodiment, main chamber section 12 is made from virgin impact-modified polypropylene copolymers and end cap 14 is made from virgin high molecular weight polyethylene. The main chamber 12 and domed end cap 14 could alternatively be made from thermoset materials. Containment system 10 is typically installed underground below a pavement layer 16, as depicted in FIG. 5. End caps or sections 14 may be provided at one or both ends of a line of interconnected chamber sections 12.

Chamber section 12 has an elliptical cross-section in a plane perpendicular to a longitudinal axis 18, along line A-A in FIG. 2. Chamber section 12 has a wall 20 provided with a plurality of longitudinally spaced, outwardly projecting corrugations 22 and a plurality of longitudinally spaced, outwardly projecting ribs 24. Corrugations 22 have flat crests or landed bights 26 with elliptical surfaces extending parallel to axis 18. Corrugations 22 further include side panels or webs 28 that are partially transverse to axis 18. At their bases along opposite sides of wall 20, corrugations 22 flare in opposing longitudinal directions and are formed with outwardly extending crest-stiffening ribs 30.

Ribs 24 alternate, or are interleaved, with corrugations 22. Ribs 24 are of smaller outside diameter than corrugations 22 and have smooth convex outer surfaces. Ribs 20 are located midway in flat valleys 32 between adjacent or successive corrugations 18.

Opposite ends of chamber section 12 are formed with a lower joint corrugation or rib 34 and an upper joint corrugation or rib 36 that enable a coupling of the chamber section 12 on a lower side to end section 14 and to another chamber section 12 on an upper side. Chamber wall 20 is further provided at opposite ends with handling ports 64 (four in number).

End section 14 comprises a substantially half-dome-shaped body member 38 having a smooth concave inner surface 40 and a smooth convex outer surface 42 that are free of reinforcement ribs or other projecting structures. Outer surface 42 is provided with recessed handgrips 44 and 46 for enabling a single individual to carry and set the end section 14 in place during installation. End section 14 further comprises an elongate longitudinally arcuate connector corrugation 48 disposed on body member 38 for coupling the body member to stormwater chamber wall 20. Body member 38 of end section 14 has a substantially half dome shape (with an elliptical form, long axis oriented vertically, short axis horizontally) with a pair of arcuate edges 50 and 60, connector corrugation 48 being disposed along upper edge 50, which extends in a vertical plane.

Connector corrugation 48 includes a pair of leg webs 52 and 54 connected to one another by a crest or bight web 56. In coupling end section 14 to chamber section 12, end-cap corrugation 48 is placed over lower joint corrugation or rib 34. As explained more fully hereinafter, this partially loose coupling (along an upper side of the end section) accommodates a limited deformation in end section 14 and facilitates a reduction in load owing to soil overarching. End section 14 is provided with three screw holes 62 (only one shown in FIG. 3) for fixing the periphery or edge 50 to chamber wall 20 to maintain a positive connection during backfilling. It is to be noted that too many screws could mitigate the slip feature. Screws are preferred through the crest and generally do not provide enough fixation to prevent the slip. Consequently, no more than 3 screws should be provided to secure the end section 14 for installation without effectively limiting slip.

Connector corrugation 48 defines an elongate channel 58 that receives the coupling rib or corrugation 34 on chamber wall 20. Through its length, channel 58 extends along a generally elliptical path and has a tapered transverse cross-section.

The domed shape of end section 14 serves to distribute compressive loads throughout the body 38 of the end section and substantially reduces, if not eliminates, internal tensile stresses. Internal stresses do not build up at any point within end section 14 but instead are directed uniformly to the periphery or perimeter 50 of the end section and transmitted therethrough to stormwater chamber wall 20.

In end section 14, soil loads on the outside surface 42 of the end section are carried more uniformly by the end section without the stress concentrations that otherwise occur at the reinforcement structures. Moreover, without reinforcing ribs, loads carried by end section 14 are more evenly distributed around upper edge or perimeter 50 of the end section and ultimately through the abutting chamber 12 to the surrounding soils.

In comparison with conventional reinforced end sections, end section 14 has more freedom to deform slightly under a soil load. As end section 14 deforms, the surrounding soils coalesce in an arched formation and carry loads that would otherwise be carried by the end section. Although reinforced shells in their entireties may be flexible, end section 14 is uniformly more flexible than the reinforced shell so that any particular area of the present end section is more flexible and there are no stress risers as there are no reinforced areas.

As discussed above, connector corrugation 48 is an elongate corrugation integral with body member 38 along edge or perimeter 50 thereof and dimensioned to fit over terminal corrugation or rib 34 of chamber wall 20. Coupling corrugation 48 cooperates with terminal corrugation or rib 34 (or 36) to loosely couple body member 38 of end section 14 to chamber wall 20 of chamber section 12 to allow for slippage between the corrugation and the corrugation or rib in a direction radial with respect to the chamber wall and the body member and transverse to the corrugation and the lip or rib.

In end section 14, soil arching also arises around the perimeter of the shell. Loads from end section 14 are transferred to the abutting chamber at the webs 52, 54, 56 of coupling corrugation 48. Since end section 14 is a separate component, not integral to chamber section 12 or bonded in any way to the chamber, the end section is allowed to slip at the bearing surface—web segments of terminal corrugation 34—against the abutting chamber section 12. The perimeter 50 of end section 14 is accordingly allowed to move radially outwardly and upwardly, relieving load in the end section. Additional movement in the direction of the load, away from the load, occurs as the web of the chamber lip, rib or corrugation 34 bends slightly. Solids around the corrugation ultimately resist loads carried in compression by the crest of the corrugation of the chamber.

As depicted in FIG. 5, a plurality of separate underground stormwater storage compartments with respective end sections 14 may be installed in parallel to one another (respective longitudinal axes 18 parallel) below pavement layer 16. Spacers (not shown) may be provided to connect laterally adjacent chamber sections 12 to one another. In one embodiment, chamber sections 12 each have a length of 90″ (2286 mm), a height of 45″ (1143 mm), and an outermost base width of 77″ (1905 mm), while end sections 14 each have a base width (perpendicular to axis 18) of 71″ (1803 mm), a base length (parallel to axis 18) of 25.5″ (673 mm) and a height of 45.1″ (1145 mm).

Per FIG. 5, the stormwater containment compartments are installed with foundation and embedment stone layers 66, 68, 70, and 70. Lowermost layer 66 is a foundation stone layer 68 below the stormwater storage chamber sections 12 and end sections 14. Lowermost layer 66 consists of clean crushed angular stone with a nominal size distribution of ¾″ to 2″ (19 mm-51 mm). Layer 66 is subjected to plate compaction or rolling to achieve a flat surface on which to set chambers and end caps. Embedment stone layer 68 surrounds the chambers 12 and end sections 14 above the foundation layer 66 and also consists of clean crushed angular stone with a nominal size distribution of ¼″ to 2″ (19 mm-51 mm). No compaction of layer 68 is required. Layer 70 consists of granular well graded soil/aggregate mixtures, less than 35% fines. Fill material for layer 70 starts from the top of embedment stone layer 68 to 18″ above the tops of chamber sections 12 and the peaks of end sections 14. Layer 70 is subjected to compaction after 12″ of material over the chambers is laid down. Compact additional layers up to 6″ (152 mm) maximum lift to a minimum 95% Standard Proctor Density. Roller gross weight should not exceed 12,000 lb (53 kN). The dynamic force applied should not exceed 20,000 lb. (89 kN). Alternatively, most pavement subbase materials can be used in lieu of layer 70. Fill material for layer 72 starts from the top of layer 70 and extends to the bottom of pavement layer 16. Layer 72 consists of any rock or soil materials, native soils or material specified by engineering plans. In general, layer 72 is prepared according to engineering plans. Paved installation may have stringent material and preparation requirements. It is recommended that there be at least 24″ of fill material from the tops or peaks of the stormwater chamber sections 12 to the bottom of a flexible pavement layer 16. For non-paved installations where rutting from vehicles may occur, a 30″ fill from the tops or peaks of the stormwater chamber sections 12 to the finished grade is recommended.

A non-woven geotextile meeting AASHTO M288 Class 2 separation requirements is to be installed to completely envelop each stormwater each containment system 10, comprising one or more chamber sections 12 and at least one end section 14, and to prevent soil intrusion into the crushed angular stone. Adjacent geotextile rolls should overlap per AASHTO M288 guidelines.

Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof. 

1. An end section for a stormwater containment assembly, comprising: a substantially half-dome-shaped body member having a smooth convex outer surface with an absence of reinforcement structures thereon and further having a smooth concave inner surface with an absence of reinforcement structures thereon; and a connector disposed on said body member along a periphery or perimeter thereof, for coupling said body member to a stormwater chamber wall.
 2. The end section defined in claim 1 wherein said connector is an elongate corrugation integral with said body member along said periphery or perimeter thereof.
 3. The end section defined in claim 2 wherein said corrugation is dimensioned to fit over a terminal lip or rib of said chamber wall.
 4. The end section defined in claim 3 wherein said corrugation cooperates with said lip or rib to loosely couple said body member to said chamber wall so as to allow for slippage between said corrugation and said lip or rib in a direction radial with respect to said chamber wall and said body member and transverse to said corrugation and said lip or rib.
 5. The end section defined in claim 4 wherein said corrugation defines a longitudinally arcuate cross-sectionally tapered channel receiving said lip or rib.
 6. The end section defined in claim 1 wherein said body member has a substantially half-dome shape with a pair of arcuate edges, said connector being disposed along one of said edges.
 7. An end section for a stormwater containment assembly, comprising: a substantially half-dome-shaped body member having a smooth convex outer surface with an absence of outwardly projecting reinforcement ribs thereon and further having a smooth concave inner surface with an absence of inwardly projecting reinforcement ribs thereon; and an elongate longitudinally arcuate corrugation integral with said body member along an edge or perimeter thereof.
 8. The end section defined in claim 7 wherein said corrugation is integral with said body member along said edge or perimeter.
 9. The end section defined in claim 8 wherein said corrugation is dimensioned to fit over a terminal lip or rib of a main chamber wall.
 10. The end section defined in claim 9 wherein said corrugation cooperates with said lip or rib to loosely couple said body member to said chamber wall so as to allow for slippage between said corrugation and said lip or rib in a direction radial with respect to said chamber wall and said body member and transverse to said corrugation and said lip or rib.
 11. The end section defined in claim 10 wherein said corrugation defines a longitudinally arcuate cross-sectionally tapered channel receiving said lip or rib.
 12. The end section defined in claim 7 wherein said body member has a pair of arcuate edges, said corrugation being disposed along one of said edges.
 13. A stormwater containment assembly, comprising: a chamber member having an arched or vaulted wall; and an end section including a substantially half-dome-shaped body member having a smooth convex outer surface with an absence of reinforcement structures thereon and further having a smooth concave inner surface with an absence of reinforcement structures thereon; and a connector disposed on said body member along a periphery or perimeter thereof, for coupling said body member to said arched or vaulted wall.
 14. The stormwater containment assembly defined in claim 13 wherein said connector is an elongate corrugation integral with said body member along said periphery or perimeter thereof.
 15. The stormwater containment assembly defined in claim 14 wherein said corrugation is dimensioned to fit over a terminal lip or rib of said arched or vaulted wall.
 16. The stormwater containment assembly defined in claim 15 wherein said corrugation cooperates with said lip or rib to loosely couple said body member to said arched or vaulted wall so as to allow for slippage between said corrugation and said lip or rib in a direction radial with respect to said arched or vaulted wall and said body member and transverse to said corrugation and said lip or rib.
 17. The stormwater containment assembly defined in claim 16 wherein said corrugation defines a longitudinally arcuate cross-sectionally tapered channel receiving said lip or rib.
 18. The stormwater containment assembly defined in claim 13 wherein said body member has a half dome shape with a pair of arcuate edges, said connector being disposed along one of said edges. 